Structural covering material



Patented May 22, 1951 Michele Croce, Evanston, Ill., assignor to Certain-Teed Products Corporation, Chicago, 111., a corporation of Maryland No Drawing. Continuation-of abandoned-application Serial No. 387,065, Aprilfi, 1941. This application June 28, 1946, Serial No. 680,086

This invention relates to covering materials, especially coverings which are intended to be exposed to the weather. The invention particularly relates to exterior coverings for walls and roofs which, in addition to affording weather protection, have structural characteristics in themselves.

This applicationis being filed as a continuation of my copending application, Serial No. 387,065,

to be careful in handling the sheets or the shinglestoprevent severe bending. V

A-quality which is desirable in such roofingjis that fora given thickness of-the sheet and weight of the sheet per unit of area, the sheet shall have acertain amount of stiffness without beingso brittle that the saturated sheet or the saturated .and coated sheet, for example when rolledin-a roll, will crack when .unrolled or bent slightly in fi1edApri15, 1941, and now ab d d, hm erection. This compromise is secured in the Covering materials, such as sheet roofing, made a ac of oofi g with a felt base mpr ith felt b se im n t d it th enated withsaturants and/coatedwithbituminous sisting material such as asphalt, and in most material yp se between rig ty h h cases coated with a weather resisting coating and l-p v lowin -1mi the Win pf thehsheet surfaced with a comminuted surfacing material or hi m therefrom d flexibility to have been used in many forms. For the impregp e cracking of the Sheet d t a d nating materials, commonly referred to in the to permit bendingas-abovementionei roofing art as saturants, bituminous materials It a been p f p heretofore to treat a or asphalts havingparticul-ar properties have fibrous base sheet with asphalts or other'bitubeen selected in order that the impregnated sheet minous materials havi the Characteristin 0f shall not be unduly subject to changes in tembeing y stiff a d ry mpe atur su 'perature occurring-with the seasons which-would p oduc s have been made in the .form of flat cause the saturant to bleed out of the sheet and Sheets as k g ts for fin and c verin thus damage or mar the roofing or the supporting materials- It also has been P p sed to imstructure. Similar care in selection is used in presnato felted sheets in various forms with conn cti ith th at resisting coatjng.a,presinous materials such as shellac, rosin, natural plied on such saturated felt base sheets to preand Synthetic resins o Various 7 k n vboth vent slidingor other'changes in the coating with p asti a d t rm settin It further has temperature which would produce defects in the been 131101908801 to incorporate at he ers i product. the paper-making process a thermoplastic resin This desirable quality of such saturants or So that --t his thermop a resin in de f m coating materials, particularly asphalts, is known will be distributed throughout the felted strucas low thermal susceptibility. It is, however, not tur of the dryfelt as it leaves t paper me possible with asphalts and'bituminous materials p ep r ry being impregnated W a bi ordinarily available, to secure a condition of minous Sat rant such as asphalt. The amount susceptibility" approaching th ideal, or ev of such thermoplastic resin which may thusbe proximating t t which is desirable The result .incorporated in a felted structure is 'limitedbeis that in most .cases a compromise is adopted by Cause Of n its inorporationvirtue of which there is used a bituminous ma- Cause Ordinary methods in a p p a ng terial or asphalt which under low temperatures, 40 process q o Suspension in a a ou ito saybelow 50'F., is hard though somewhat brittle water such a resin could not be incorporate'd'at but at high temperatures, say above 100 F., is the beater in an amount substantially'in excess somewhat softened-although not to the degree of 50% of the fiber weight in'the'felte'd' sheet. that it will readily flow. With bituminous ma- It s an Object (if the n o D o fle terials, particularly asphalt, the range of temcovering material'which will'have a substantial peratures within which such qualities may be se- Stiffness de a y d a e *of temp racured is generally between 40 and 150 F. These tures,,particularly the range of atmospherictemconditions of becoming brittle when cold and fluid peratures experienced" throughou h y when hot must be dealt with in roofing manu- It is also an object .of the invention to secure facture utilizing bituminous or asphaltic main such a product a resistance to cracking or terials. A certain amount of softenin occurs in breaking under'fiexing stress. theroof-in summer'temperatures and the roofing It isa further-object of the inventionto acbecomes more brittle than is desirable under complish these results in asheet utilizing orwinter temperatures. This makes it necessary dinary felt base materials. in laying, roofing in coldweather in-many cases -It is afurtherobjectof the invention to secure these properties in a rigid sheet material which will afford adequate resistance to the weather and to the action of light and heat.

According to the invention in its broad aspects a felted sheet, preferably as ordinarily made in the paper-making process, is impregnated with a thermoplastic resin to secure the desired stiffening of the felted sheet and resistance to softening under high temperatures. The sheet also may be impregnated with a bituminous material, particularly asphalt, which will afford weather resistance and at the same time provide a desirable resistance to cracking. A characteristic of such a bituminous material or such an asphalt for the purposes of the invention is that it shall have a low penetration, that is, the quality of maintaining its solidity and resistance to plastic flow or deformation at ordinary temperatures and below ordinary temperatures. Such a characteristic in an asphalt is secured, however, at the expense of increased thermal susceptibility. Thus atthe higher temperatures to which such covering materials may be subjected such an asphalt would tend to become more plastic and of greater fluidity than is desirable. A sheet impregnated with such an asphalt would become too flexible and lose its resistance to bending. In some cases at vthe higher temperatures, such as may be experienced in tropical countries, the asphalt might ooze or run from the sheet. In view also of the purpose of the invention to provide a sheet material which will have structural characteristics, it is important that the rigidity of the sheet shall be substantially maintained throughout the range of temperatures to which the structure is subjected and that the fluid condition of the impregnating materials be not developed.

The function of the thermoplastic resin above referred to, therefore, is that it shall coact with the thermoplastic bituminous material, commonly asphalt, to maintain the rigidity of the sheet and prevent flow and softness at the higher temperatures to which the sheet is to be subjected. Resins of various kinds may be used, examples of which will be hereafter given, but a resin is chosen which substantially will maintain its penetration without great variation throughout the ordinary range of temperatures above given, viz.: 40 and 150 F. Particularly with the resinous material commercially known as Vinsol the penetration remains substantially constant throughout this range. Thus with a, felted sheet impregnated with both the resin and the asphalt the cooperation of these two impregnating materials secures the qualities above described which are desirable for a structural sheet. According to the invention the felted sheet is impregnated with the impregnating materials in molten condition. It is common practice to heat asphalt to fluid condition for impregnating felted sheets in roofing manufacture. It is further within the knowledge and skill of the art to impregnate felted sheets with resins in molten condition. In the practice of the invention these impregnating materials may be mixed together during the operation of melting them so that they may be delivered to or applied to the dry felt simultaneously as a mixture. Within the scope of the invention, however, these materials may be applied to the sheet separately, either one of them before the other, to impregnate the sheet with the desired or requisite amount of each of the impregnating materials.

By the method of impregnating a sheet with the resin and with the asphalt in molten condi- 4 tion a much higher percent of impregnation may be secured than by incorporating the materials at the beater, for example. Thus it is possible to impregnate an ordinary dry felt intended for roofing manufacture with molten asphalt in the amount of 175% to 200% or more of asphalt based on the weight of the dry felt. It is also possible to impregnate such a felt with the resin in the amount of 175% to 200% or more. For the purpose of the invention the amount of either impregnating material may be varied between 25% and 75% of the total amount of impregnating material. Thus the amount of either ingredient based on the weight of the dry felt, when for example the total impregnation is 200%, would be between 50% and These proportions and relations of the impregnating materials represent those which are preferable for securing the requisite cooperation of the two materials to obtain the two otherwise opposed characteristics in the sheet, viz.: rigidity and resistance to cracking. With a greater amount of the resin and therefore less of the, asphalt, the sheet may become too brittle and too subject to cracking. With greater amounts of asphalt and less of resin insufficient stiffness for structural purposes of the sheet may result.

For the purposes of the invention the asphalts for impregnating the felted sheet may have ranges of penetration and melting point (softening point) as in the following table:

The penetration test as given in the above table is made by the American Society for Testing Materials Test D525, as given in the 1939 Standards, Part II, Non-Metallic MaterialsConstructional, page 412, Method of Testing for Penetration of Bituminous Materials.

For practical reasons asphalts will be used for the purposes of the invention as in ordinary roofing manufacture which have a flash point not substantially less than 450 F. to prevent ignition causing fire. The asphalts may be selected as in roofing manufacture so that their viscosity at temperatures to which they may be heated above the melting point, namely 350-450 F. without the risk of burning the base felt will secure the necessary fluidity for impregnating the felt and to secure the proper degree of saturation thereof in the ordinary processes and with the ordinary apparatus used in manufacture of roofing.

Also for the purpose of the invention these properties for the thermoplastic resin may lie within the following ranges:

The penetration for the resin known as Vinsol which will be hereafter further described and which is particularly suitable for the purposes of the invention was found to be substantially be- 5 tween and 2 for :all the temperatures at which tests were 'made, namely 77, 115, 135, and 150 F. The melting point of this Vinsol resin is about 240 F. and the softeningpoint 235 F.

The method of test of penetration for the resins is the same as that referred to above, namely the American Society for Testing Mate-.- rials test for asphalt, except that in all cases the weight used to effect the penetration was 100 grams and the time5 seconds for all temperatures. This modification of the test was adapted in view of the low penetration value of these resins.

The respective materials, i. e., asphalt and resin, selected to have these .characteristicsand used as impregnatingmaterials in the roofing felt make it possible to secure in the finished sheet a product which will have the requisite stiffness at the ordinary hightemperaturewhich such roofing may acquire under summer sun, viz., of the degree .of 175 F., and alsonot to become too brittle for handling and under load when placed in the structure atlow winter temperatures.

A sheet of. felt impregnated with the two kinds of materials, as above described, may be used for producing corrugated-sheets. For this purpose the sheets maybe impregnated with amixture of molten resin and asphalt-and while the sheet is still hot may be pressed in a corrugated mold or othersuitable mechanical'devi'ce formed with the corrugations or with such other contour as will. produce a mechanical form desired for the structuralpurpose. The corrugated sheet may then be allowed to cool to permit the thermoplastic content thereof to set. The result will be a corrugated sheet material which is of marked stiffness, not only because its corrugated form is-maintained by the impregnating materials but also because of the inherent stifi character of the impregnated and set sheet itself. Such a corrugated sheet, moreover, willhave weather-resisting properties by virtue of the asphalt impregnation and will be resistant to cracking or breakingbecause of the presence ofthe asphalt.

The sheet-material of 'the'invention produced in the manner above described, if desired-maybe further treated with a weather and water resisting coating, such as asphalt, applied to the surface of the sheet. The impregnated sheet without asphalt coating thereon may have applied thereto a coating of metallic paint, such as aluminum paint, in order to afford heat reflection or the asphalt coated impregnated sheet may be coated with a metallic paint or may be surfaced with metallic flakes or powder. The asphalt coated sheet in some cases may be surfaced with mineral particles, such as those ordinarily applied to roofing sheets.

Ordinary roofing felts are particularly desirable for the purposes of the invention because they may be made in the paper-making process commonly used in roofing manufacture. For some purposes, however, such roofing felts which ordinarily vary in caliper from .025" to .080" will not as a single sheet provide sufficient thickness for the covering in the form of a fiat sheet or as a corrugated sheet. Two or more of such roofing felts impregnated in accordance with the invention with a composite resin and asphalt material, therefore, may be laminated together to secure the increased thickness. Preferably these sheets are laminated together with an adhesive, especially asphalt, binding them together. Moreover it is the particular advantage of the laminated :form of the invention that the rigidity desired is obtained by virtue of the composite impregnating material but that the tendency to crack or to wrinkle at the surface-of the sheet is reduced'because of the limitation of the thickness of the laminations. This avoidance of cracking or wrinkling is thought to be due in part to the interposed layer of therplastic adhesivematerial between the laminations which layer, while holding the sheets'strongly, reduces because of its plastic quality the amount of s'tretchor'of compression at the surfaces of the individual laminations which produces cracking and :wrinkling. This characteristic is especially desirable for the formation of corrugated sheets because in the process of forming the corrugations the amount of stretch which takes place in each of the laminations at each corrugation is' -thus limited. The impregnated sheet thus remains substantially in the form in which it was produced and the cooperation of the impregnating resin: and the impregnatingasphalt with each other and with the fibrous structure of the felt remains substantially undisturbed. There being no substantial cracking or wrinkling in the coated impregnated sheet, the weather-resisting property and the structural characteristic thereof thus are maintained.

The thermoplastic resins utilized in the invention'of which Vinsol, above mentioned, is a commericalexample, may be natural resins or synthetic resins which have the physical properties given in Table II above. As examples of such resins may be given'the following:

Table III Melting Softengrigl Point, Pgmt East India Macassar 214-252.

By ester gum is commonly understood an ester of rosin and glycerine, this .product being well known in the varnish industry.

In addition to the above and preferred for the purposes of the invention the resin known as Vinsol which is commercially available has a low penetration as given in connection with Table 11 above and also has a low susceptibility. This resin may be melted, however, at about 240 F. and may be used in this melted condition to impregnate the felt in the same manner as is practiced with asphalt in roofing manufacture. The fluidity of the resin necessary for impregnation may be attained above the melting point but below the normal impregnating temperatures of between 350 and 450 F. as in the ordinary roofing manufacture. The resin in the melted condition is miscible with melted'asphalt. If desired, however, the materials in sufficiently divided form may be mixed dry and then melted. The functions which have been referred to above for the two types of impregnating materials for the purposes of the invention may be secured by either method of preparation for impregnation.

Vinsol is prepared by extracting from the wood of stumps of southern long-leaf pine by the use of selective solvents the resinous materials contained in the wood. The stumps are first chipped and digested with benzene. The materials thus dissolved in the processes of digestion are fractionated to remove the lighter fractions, that is, the solvent, turpentine, pine oil, etc. The residue remaining from the fractionation is a mixture of the Vinsol resin and other resins.

This composite material is then subjected to a further extraction process which consists of successive treatments with two immiscible solvents, furfural and naphtha. The Vinsol resin is very soluble in furfural whereas the other resins are not. Successive washings are made to purify the Vinsol resin which may be secured in the solid state by evaporation of the furfural solvent. The Vinsol resin may be defined as the extractive product derived by furfural extraction of the residue from the benzene extraction of chips from stumps of southern longleaf pine.

Thus the invention may provide a water-resistant covering material in different forms which, because of the composite impregnation, are of low thermal susceptibility at the same time having the requisite rigidity, resistance to fracture and strength for building purposes. Moreover, such sheets may be made penetrable for fasteners so as to be readily fastened to the supporting structure by the fasteners driven therethrough. The sheets thus may be used as are sheets of ordinary roofing materials or as are sheets of corrugated sheet metal. In the case of fiat sheets of the invention the fasteners, if desired, may be sealed with a sealing cement, as in some cases is done with roofing sheets. In the case of the corrugated sheets the fasteners preferably are driven through the sheet at the peak of the corrugation so that the water will shed from the fastener. Moreover, as in applying corrugated sheet metal, nails having a flexible or deformable washer may be used. By virtue of the plastic characteristic of the roofing material itself, or the asphalt coating carried thereby, such fasteners may become slightly embedded in the surface of the sheet or the impregnating or the coating materials may close around the fastener by plastic flow to assist in securing wa- 4 change in flexibility throughout a temperature range of from low winter temperatures to about 175 F. adapted for use as roofing material comprising a base of felted fibrous material and impregnating material incorporated by absorption in said base and comprising pressure tar asphalt and a resin which is the portion of the resinous material of southern long-leaf pine which is soluble in benzene and in furfural but is insoluble in naphtha, each of said impregnating materials comprising from about 25% to about by weight of the impregnating material.

2. Sheet material comprising a base of felted fibrous material, and impregnating material incorporated by absorption in said base and comprising a resin which is the portion of the resinous material of southern long-leaf pine which is soluble in benzene and in furfural but is insoluble in naphtha and pressure tar asphalt having a penetration value at F. of between 5 and 50 and a softening point between F. and 225 F., with each ingredient comprising from 25% to 75% by weight of the impregnating material.

MICHELE CROCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 202,902 Warren Apr. 23, 1878 1,849,867 Eckert Mar. 15, 1932 1,949,255 Keller Feb. 27, 1934 2,094,709 Kinney Oct. 5, 1937 2,105,087 Lutz Jan. 11, 1938 ,13 ,204 Marc Jan. 23, 1940 2,188,478 Lynn Jan. 30, 1940 2,204,772 Rivkin June 18, 1940 2,223,289 Lyons Nov. 26, 1940 2,346,947 Schlaanstine Apr. 18, 1944 OTHER REFERENCES Vinsol Resin, Its Characteristics and Some Suggested Uses, p. 18, pub. 1937, Hercules Powder 00., Wilmington, Del. 

1. SHEET MATERIAL OF LOW SUSCEPTIBILITY TO CHANGE IN FLEXIBILITY THROUGHOUT A TEMPERATURE RANGE OF FROM LOW WINTER TEMPERATURES TO ABOUT 175* F. ADAPTED FOR USE AS ROOFING MATERIALS COMPRISING A BASE OF FELTED FIBROUS MATERIAL AND IMPREGNATING MATERIAL INCORPORATED BY ABSORPTION IN SAID BASE AND COMPRISING PRESSURE TAR ASPHALT AND A RESIN WHICH IS THE PORTION OF THE RESINOUS MATERIAL OF SOUTHERN LONG-LEAF PINE WHICH IS SOLUBLE IN BENZEND AND IN FURFURAL BUT IS INSOLUBLE IN NAPHTHA, EACH OF SAID IMPREGNATING MATERIALS COMPRISING FROM ABOUT 25% TO ABOUT 75% BY WEIGHT OF THE IMPREGNATING MATERIAL. 